Localized multicast in a low power and lossy network based on rank-based distance

ABSTRACT

In one embodiment, a method comprises: identifying, by a low power and lossy network (LLN) device in a low power and lossy network, a minimum distance value and a distance limit value for limiting multicast propagation, initiated at the LLN device, of a multicast data message in the LLN; and multicast transmitting, by the LLN device, the multicast data message with a current distance field specifying the minimum distance value and a distance limit field specifying the distance limit value, the multicast transmitting causing a receiving LLN device having a corresponding rank in the LLN to respond to the multicast data message by: (1) determining an updated distance based on adding to the current distance field a rank difference between the receiving LLN device and the LLN device, and (2) selectively retransmitting the multicast data message if the updated distance is less than the distance limit value.

TECHNICAL FIELD

The present disclosure generally relates to localized multicast in a lowpower and lossy network based on rank-based distance.

BACKGROUND

This section describes approaches that could be employed, but are notnecessarily approaches that have been previously conceived or employed.Hence, unless explicitly specified otherwise, any approaches describedin this section are not prior art to the claims in this application, andany approaches described in this section are not admitted to be priorart by inclusion in this section.

A Low-power and Lossy Network (LLN) is a network that can include dozensor thousands of low-power router devices configured for routing datapackets according to a routing protocol designed for such low power andlossy networks (RPL): such low-power router devices can be referred toas LLN devices or “RPL nodes”. Each RPL node in the LLN typically isconstrained by processing power, memory, and energy (e.g., batterypower); interconnecting wireless links between the RPL nodes typicallyare constrained by high loss rates, low data rates, and instability withrelatively low packet delivery rates. A network topology (a “RPLinstance”) can be established based on creating routes in the form of adirected acyclic graph (DAG) toward a single “root” network device, alsoreferred to as a “DAG root” or a “DAG destination”. Hence, the DAG alsois referred to as a Destination Oriented DAG (DODAG). Network trafficmoves either “up” towards the DODAG root or “down” towards the DODAGleaf nodes.

The constraints in processing power, memory, and energy in the RPL nodesdescribed above also prevent a given RPL node from maintaining amulticast routing topology, especially since the inherently dynamicproperties in the wireless links prevent the RPL nodes from maintainingany multicast routing topology in response to dynamic changes in thewireless links.

Hence, a substantial problem is that multicast transmission of amulticast data message within an LLN utilizing a DODAG-based topologyand comprising thousands of LLN devices can cause substantialinterference for LLN devices that have no need for the multicast datamessage, for example where the multicast data message is intended onlyfor LLN devices located within a relatively small subDAG within the LLN.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the attached drawings, wherein elements having thesame reference numeral designations represent like elements throughoutand wherein:

FIG. 1 illustrates an example low power and lossy network (LLN) havingan apparatus configured for limiting propagation of a multicast datamessage in the LLN, according to an example embodiment.

FIG. 2 illustrates another example low power and lossy network (LLN)having one or more network devices configured for limiting propagationof a multicast data message in the LLN, according to an exampleembodiment.

FIG. 3 illustrates an example implementation of any of the networkdevices of FIG. 1 or 2, according to an example embodiment.

FIGS. 4A-4C illustrates an example method of limiting propagation of amulticast data message in the LLN, according to an example embodiment.

FIG. 5 illustrates an example multicast transmission of a multicast datamessage initiated by an LLN device operating as a multicast origin,according to an example embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS OVERVIEW

In one embodiment, a method comprises: identifying, by a low power andlossy network (LLN) device in a low power and lossy network, a minimumdistance value and a distance limit value for limiting multicastpropagation, initiated at the LLN device, of a multicast data message inthe LLN; and multicast transmitting, by the LLN device, the multicastdata message with a current distance field specifying the minimumdistance value and a distance limit field specifying the distance limitvalue, the multicast transmitting causing a receiving LLN device havinga corresponding rank in the LLN to respond to the multicast data messageby: (1) determining an updated distance based on adding to the currentdistance field a rank difference between the receiving LLN device andthe LLN device, and (2) selectively retransmitting the multicast datamessage if the updated distance is less than the distance limit value.

In another embodiment, one or more non-transitory tangible media encodedwith logic for execution by a machine and when executed by the machineoperable for: identifying, by the machine implemented as a low power andlossy network (LLN) device in a low power and lossy network, a minimumdistance value and a distance limit value for limiting multicastpropagation, initiated at the LLN device, of a multicast data message inthe LLN; and multicast transmitting, by the LLN device, the multicastdata message with a current distance field specifying the minimumdistance value and a distance limit field specifying the distance limitvalue, the multicast transmitting causing a receiving LLN device havinga corresponding rank in the LLN to respond to the multicast data messageby: (1) determining an updated distance based on adding to the currentdistance field a rank difference between the receiving LLN device andthe LLN device, and (2) selectively retransmitting the multicast datamessage if the updated distance is less than the distance limit value.

In another embodiment, a method comprises: receiving, by a receiving lowpower and lossy network (LLN) device in a low power and lossy network,one or more multicast data messages from respective one or moreneighboring transmitting LLN devices in the LLN; detecting, by thereceiving LLN device among the one or more multicast data messages, alowest distance value in a current distance field and a distance limitvalue in a distance limit field, the lowest distance value indicating amulticast transmission distance of the corresponding one neighboringtransmitting LLN device relative to a multicast origin of the one ormore multicast data messages; determining, by the receiving LLN device,an updated distance to the multicast origin based on adding to thelowest distance value a rank difference between the correspondingneighboring transmitting LLN device and the receiving LLN device; andselectively multicast transmitting, by the receiving LLN device, themulticast data message based on determining the updated distance is lessthan the distance limit value that limits multicast propagation, theselectively multicast transmitting including updating the currentdistance field with the updated distance value prior to transmission.

In another embodiment, one or more non-transitory tangible media encodedwith logic for execution by a machine and when executed by the machineoperable for: receiving, by a machine implemented as a receiving lowpower and lossy network (LLN) device in a low power and lossy network,one or more multicast data messages from respective one or moreneighboring transmitting LLN devices in the LLN; detecting, by thereceiving LLN device among the one or more multicast data messages, alowest distance value in a current distance field and a distance limitvalue in a distance limit field, the lowest distance value indicating amulticast transmission distance of the corresponding one neighboringtransmitting LLN device relative to a multicast origin of the one ormore multicast data messages; determining, by the receiving LLN device,an updated distance to the multicast origin based on adding to thelowest distance value a rank difference between the correspondingneighboring transmitting LLN device and the receiving LLN device; andselectively multicast transmitting, by the receiving LLN device, themulticast data message based on determining the updated distance is lessthan the distance limit value that limits multicast propagation, theselectively multicast transmitting including updating the currentdistance field with the updated distance value prior to transmission.

In another embodiment, one or more non-transitory tangible media encodedwith logic for execution by a machine and when executed by the machineoperable for: limiting multicast propagation of a multicast data messagein a low power and lossy network (LLN) based on setting, by the machineimplemented as a root network device in the LLN, a distance limit valuefor limiting the multicast propagation; and unicast transmitting, by theroot network device, a unicast message containing the multicast datamessage and the distance limit value to an LLN device via the LLN, theunicast message causing the LLN device to multicast transmit themulticast data message with a current distance field specifying aminimum distance value of the LLN device and a distance limit fieldspecifying the distance limit value; wherein the limiting multicastpropagation in the LLN is based on the multicast data message causing areceiving LLN device having a corresponding rank in the LLN to: (1)determine an updated distance based on adding to the current distancefield a rank difference between the receiving LLN device and the LLNdevice, and (2) selectively retransmit the multicast data message if theupdated distance is less than the distance limit value, wherein thereceiving LLN device suppresses any transmission of the multicast datamessage if the updated distance is not less than the distance limitvalue.

DETAILED DESCRIPTION

Particular embodiments enable scalable and localized propagation ofmulticast data messages in a low power and lossy network (LLN) utilizinga DODAG-based topology, for example according to the InternetEngineering Task Force (IETF) Request for Comments (RFC) 6550 and/or RFC7731, where rank-based distance limit values can be used for limiting(i.e., localizing) multicast propagation to within an identifiable areain the DODAG topology. The example embodiments enable the multicastpropagation range in the LLN to be defined based on an identifiableobjective function (OF), enabling the multicast propagation range(limited by a distance limit value relative to a multicast origindevice) to be established according to the DODAG topology and/or amulticast routing topology having its own corresponding objectivefunction.

Hence, the example embodiments enable localized multicast based on arank-based distance limit value, enabling multicast to be confinedwithin a prescribed portion of the DODAG topology.

The example embodiments can be particularly effective in limitingmulticast propagation to within an identifiable physical location, forexample limiting multicast propagation of a multicast message to anidentifiable room (e.g., a meter “vault”) containing multiple CG-meshbased metering devices for respective apartment dwelling units in alarge apartment building, where the CG-mesh based metering devices inthe meter “vault” are part of a large-scale CG-mesh networkinfrastructure comprising hundreds or thousands of meter “vaults” acrossa large city in an electrical grid. In this example, a networkmanagement device in the CG-mesh based infrastructure (providingelectrical grid metering for the large city) can implement projectedlocalized multicast based on unicast transmission of a unicast message(comprising the multicast message and associated distance limit value)to a destination multicast origin within the meter “vault”: themulticast origin can respond to the unicast message by multicasttransmitting the multicast data message with the distance limit value,enabling multicast propagation of the multicast data message to beconfined within the meter “vault” based on the associated rank values ofthe CG-mesh metering devices within the vault relative to the multicastorigin and the distance limit value.

FIGS. 1 and 2 are diagrams illustrating an example low power and lossynetwork (LLN) 10 having a root network device 12 and LLN devices (e.g.,“A” through “W”) 14, also referred to as RPL devices or RPL networkdevices 14, according to an example embodiment. The LLN 10 can beimplemented as an Internet Protocol version 6 (IPv6) wireless radiofrequency (RF) mesh network, deployed for example using wireless linklayer protocols such as IEEE 802.15.4e and/or IEEE 802.15.4g (referredto herein as “IEEE 802.15.4e/g”). In particular, the LLN 10 can beimplemented as a smart grid Advanced Metering Infrastructure (AMI)network that can utilize a connected grid mesh (CG-Mesh) that comprisesa field area router (FAR) implemented as a root network device 12 andthousands of LLN devices 14, where each LLN device 14 can possiblyreach, within its transmission range of its corresponding wireless datalink 16, hundreds of neighboring LLN devices 14. The root network device12 can be implemented, for example, based on a commercially-availableCisco® Connected Grid Router (CGR) such as the CGR 1000 Series,commercially available from Cisco Systems, San Jose, Calif., modified asdescribed herein.

A Low-Power and Lossy Network (LLN) 10 typically operates with strictresource constraints in communication, computation, memory, and energy.Such resource constraints may preclude the use of existing IPv6multicast routing and forwarding mechanisms. Traditional IP multicastdelivery typically relies on topology maintenance mechanisms to discoverand maintain routes to all subscribers of a multicast group. However,maintaining such topologies in LLNs is costly and may not be feasiblegiven the available resources.

Memory constraints may limit LLN devices 14 to maintaining links and/orroutes to one or a few neighbors, hence RPL according to RFC 6550specifies both storing and non-storing modes: non-storing mode enables aRPL network device 14 to maintain only one or a few default routestowards an LLN Border Router (LBR) (i.e., root network device) 12 anduse source routing to forward messages away from the LBR. The memoryconstraints also prevent an LLN device 14 from maintaining a multicastrouting topology.

A network topology (e.g., a “RPL instance” according to RFC 6550) 20 canbe established based on creating routes toward a single “root” networkdevice (e.g., a backbone router) 12 in the form of a directed acyclicgraph (DAG) toward the DAG root 12, where all routes in the LLN 10terminate at the DAG root 12 (also referred to as a “DAG destination”).Hence, the DAG also is referred to as a Destination Oriented DAG (DODAG)20. Network traffic can move either “up” towards the DODAG root 12 or“down” away from the DODAG root 12 and towards the DODAG leaf nodes(e.g., leaf nodes “J”, “K”, “O”, “T”, etc.). The root network device 12can output RPL-based DODAG Information Object (DIO) messages accordingto RFC 6550 and specifying an identified objective function (OF) andassociated topology network metrics (including a DODAG rank of theadvertising root network device 12), for formation of a DODAG-basednetwork topology 20 that supports multicast operations.

A “child” network device detecting the DIO can select the DAG root 12 asa parent in the identified DODAG 20 based on comparing network topologymetrics (advertised in the DIO) to an identifiable objective function ofthe RPL instance (e.g., specified in the DIO). The “child” networkdevice, upon attaching to its parent, can output its own DIO withupdated network topology metrics (including an updated DODAG rank) thatenable other RPL network devices 14 to discover the DODAG 20, learn theupdated network topology metrics, and select a DODAG parent.

As described in RFC 6550, each RPL network device 14, in response to theroot network device 12 and/or a parent RPL network device 14 in thetree-based DODAG topology 20, can execute an objective function (OF)specified in the DIO message that enables the RPL network device 14 todetermine its own “rank” within the DODAG topology 20, where the rootnetwork device 12 can be allocated a relatively low-valued rank (e.g.,“1”), and a next-hop LLN device (e.g., “A” or “B”) can calculate arelatively-higher rank (e.g., “20”) based on the corresponding rank ofthe parent root network device 12 (specified in the received DIOMessage) and topology-based metrics associated with execution of the OF.Hence, a LLN device 14, in response to attaching to the root networkdevice 12, can output an updated DIO message specifying thecorresponding “rank” of the RPL network device 14 relative to the rootnetwork device 12, enabling other network devices to join the tree-basedDODAG topology 20 resulting in the tree-based DODAG topology. Hence, achild (e.g., “C”) 14 can use the identified objective function andcalculate for itself a higher rank (e.g., “50”) relative to thecorresponding rank (e.g., “20”) advertised by its parent (e.g., “B”),and output an updated DIO specifying the corresponding rank (e.g.,“50”), enabling the next child device (e.g., “F”) 14 to calculate itsown corresponding rank (e.g., “100”), etc.

Hence, a LLN device 14 can calculate its own rank within the DODAG 20based on executing the objective function identified in the received DIOmessage, and based on the advertised rank and advertised metrics fromthe received DIO message, detected attributes (e.g., Received SignalStrength Indicator (RSSI)) associated with reception of the DIO message,prescribed constraints or policies set in the LLN device 14 (e.g.,minimum/maximum permitted rank values, etc.). Hence the “rank” used by aLLN device 14 can identify a relative positional priority of the LLNdevice 14 within the LLN device 14, but is distinct from a hop countvalue: in other words, a “hop count” is not and cannot be used as a“rank” as described herein because a “rank” monotonically increases awayfrom the root network device 12 for formation of the DODAG 20, and the“rank” is determined based on execution of an identified objectivefunction (and therefore can have a nonlinear increase in rank values).Additional details regarding calculating a rank value can be found, forexample, in Section 8.2 of RFC 6550.

Downward routes (i.e., away from the DAG root 12) can be created basedon Destination Advertisement Object (DAO) messages that are created by aRPL node 14 and propagated toward the DAG root 12. The root networkdevice 12 generating the RPL instance 20 can implement downward routesin the DAG 20 of the LLN 10 in either a storing mode only (fullystateful), or a non-storing mode only (fully source routed by the DAGroot). In storing mode, a RPL node 14 unicasts its DAO message to itsparent node, such that RPL nodes 14 store downward routing table entriesfor their “sub-DAG” (the “child” nodes connected to the RPL node). Innon-storing mode the RPL nodes 14 do not store downward routing tables,hence a RPL node 14 unicasts its DAO message to the DAG root 12, suchthat all data packets are sent to the DAG root 12 and routed downwardwith source routes inserted by the DAG root 12.

Although only the RPL network devices “A”, “B”, “C”, “D”, and “R” arelabeled with the reference numeral “14” to avoid cluttering in theFigures, it should be apparent that all the RPL network devices “A”through “W” are allocated the reference numeral “14” for purposes of thedescription herein. Further, it should be apparent that all the networkdevices “A” through “W” 14 are configured for establishing wireless datalinks 16 and DODAG parent-child connections 18 (collectively “wirelessDODAG parent-child connections”), even though only the wireless DODAGparent-child connections 18 between the root network device 12 and theRPL network devices “A” and “D” 14 are labeled with the referencenumeral “18” (and only the wireless data links 16 of the root networkdevice 12 and the RPL network devices “A” and “D” are labeled) to avoidcluttering in the Figures.

Conventional deployments of the RPL protocol (e.g., according to RFC6550) can suffer from many inefficiencies in a DAG network topology 20in LLNs 10 that contain thousands of network devices 14 that are denselydeployed in the data network 10. In one example, unrestrictedpropagation of multicast messages downward in the DODAG 20 of the LLN 10can enable the root network device 12 to propagate critical managementmessages to all LLN devices 14, however such unrestricted propagationcan create substantial traffic loads in the LLN 10; hence, unrestrictedmulticasting from the root network device 12 is not scalable in the LLN10 due to the substantial traffic loads that would be encountered.

Moreover, non-root initiated multicasting (i.e., initiated by an LLNdevice 14) can result in unwanted propagation of multicast messagesthroughout the LLN 10, including multicasting to LLN devices 14 thathave no need for the multicast messages; such unwanted propagation ofmulticast messages also can create security issues by enabling roguenetwork devices to detect multicast messages from any location in theLLN 10. As illustrated in FIGS. 1 and 2, the network devices “L” through“W” are illustrated as positioned within a limited region 22 of the LLN10, for example within an underground room of an apartment building,where the limited region 22 can be used for deployment of a meter“vault” comprising multiple CG-mesh based metering devices “L” through“W” 12 for respective above-ground apartment dwelling units in a largeapartment building, where the network device “L” serves as the gatewaybetween the “vault” 22 and the CGI network 10. Hence, unrestrictedpropagation of a multicast message 24 that is relevant only to theCG-mesh metering devices “L” through “W” 14 in the limited region 22could cause undesirable traffic congestion outside the limited region 22(e.g., if the multicast data message 24 was multicast transmitted by theCG-mesh metering device “L” 14 to its “gateway” device “F” outside thelimited region 22), and could result in additional security risks byexposing the network devices “L” through “W” to potential rogue networkdevices outside the limited region 22.

Hence, the example embodiments described herein enable localizedmulticast based on a rank-based distance limit value, enablingpropagation of multicast messages 24 to be confined within a limitedregion 22 of the DODAG topology 20. As described below, the rank-baseddistance limit value can cause the LLN device “L” (and/or “F”) 14 tosuppress any multicast transmission of the multicast data message 24outside the limited region 22 based on its rank in the limited region 22relative to the rank-based distance limit value relative to themulticast origin “R”.

Hence, the example embodiments described herein enable localizedmulticast within a limited region 22 of the DODAG 20, enabling maximaluse of localized multicasting while maintaining network security andpreventing transmissions outside the limited region 22. As describedbelow, the multicast propagation may be initiated by a multicast origindevice “R” 14 generating the multicast data message 24 as illustrated inFIG. 1.

As illustrated in FIG. 2 and as described in further detail below, themulticast propagation also can be initiated based on the root networkdevice 12 “tunneling” to the multicast origin device “R” 14 a unicastdata packet 26 that comprises at least the payload of the multicastmessage, and that also can include the rank-based distance limit valuethat can limit propagation of the multicast data message 24 to withinthe limited region 22. Hence, the root network device 12 can initiate aprojected localized multicast of a multicast data message 24 within aspecific limited region 22, enabling distribution of location-specificmetering instructions (e.g., control data for a specific apartmentbuilding, software updates on a per-building basis, etc.) in a scalablemanner.

FIG. 3 illustrates an example implementation of any of the networkdevices 12, 14 of FIG. 1 or 2, according to an example embodiment. Eachapparatus 12, 14 is a physical machine (i.e., a hardware device)configured for implementing network communications with other physicalmachines via the LLN 10. The term “configured for” or “configured to” asused herein with respect to a specified operation refers to a deviceand/or machine that is physically constructed and arranged to performthe specified operation.

Each apparatus 12, 14 can include a device interface circuit 30, aprocessor circuit 32, and a memory circuit 34. The device interfacecircuit 30 can include one or more distinct physical layer transceiversfor communication with any one of the other devices 12, 14; the deviceinterface circuit 30 also can include an IEEE based Ethernet transceiverfor communications with the devices of FIG. 1 via any type of data link(e.g., a wired or wireless link, an optical link, etc.). The processorcircuit 32 can be configured for executing any of the operationsdescribed herein, and the memory circuit 34 can be configured forstoring any data or data packets as described herein.

Any of the disclosed circuits of the devices 12, 14 (including thedevice interface circuit 30, the processor circuit 32, the memorycircuit 34, and their associated components) can be implemented inmultiple forms. Example implementations of the disclosed circuitsinclude hardware logic that is implemented in a logic array such as aprogrammable logic array (PLA), a field programmable gate array (FPGA),or by mask programming of integrated circuits such as anapplication-specific integrated circuit (ASIC). Any of these circuitsalso can be implemented using a software-based executable resource thatis executed by a corresponding internal processor circuit such as amicroprocessor circuit (not shown) and implemented using one or moreintegrated circuits, where execution of executable code stored in aninternal memory circuit (e.g., within the memory circuit 34) causes theintegrated circuit(s) implementing the processor circuit to storeapplication state variables in processor memory, creating an executableapplication resource (e.g., an application instance) that performs theoperations of the circuit as described herein. Hence, use of the term“circuit” in this specification refers to both a hardware-based circuitimplemented using one or more integrated circuits and that includeslogic for performing the described operations, or a software-basedcircuit that includes a processor circuit (implemented using one or moreintegrated circuits), the processor circuit including a reserved portionof processor memory for storage of application state data andapplication variables that are modified by execution of the executablecode by a processor circuit. The memory circuit 34 can be implemented,for example, using a non-volatile memory such as a programmable readonly memory (PROM) or an EPROM, and/or a volatile memory such as a DRAM,etc.

Further, any reference to “outputting a message” or “outputting apacket” (or the like) can be implemented based on creating themessage/packet in the form of a data structure and storing that datastructure in a non-transitory tangible memory medium in the disclosedapparatus (e.g., in a transmit buffer). Any reference to “outputting amessage” or “outputting a packet” (or the like) also can includeelectrically transmitting (e.g., via wired electric current or wirelesselectric field, as appropriate) the message/packet stored in thenon-transitory tangible memory medium to another network node via acommunications medium (e.g., a wired or wireless link, as appropriate)(optical transmission also can be used, as appropriate). Similarly, anyreference to “receiving a message” or “receiving a packet” (or the like)can be implemented based on the disclosed apparatus detecting theelectrical (or optical) transmission of the message/packet on thecommunications medium, and storing the detected transmission as a datastructure in a non-transitory tangible memory medium in the disclosedapparatus (e.g., in a receive buffer). Also note that the memory circuit34 can be implemented dynamically by the processor circuit 32, forexample based on memory address assignment and partitioning executed bythe processor circuit 32.

FIGS. 4A-4C illustrate an example method of limiting propagation of amulticast data message in the LLN, according to an example embodiment.The operations described with respect to any of the Figures can beimplemented as executable code stored on a computer or machine readablenon-transitory tangible storage medium (i.e., one or more physicalstorage media such as a floppy disk, hard disk, ROM, EEPROM, nonvolatileRAM, CD-ROM, etc.) that are completed based on execution of the code bya processor circuit implemented using one or more integrated circuits;the operations described herein also can be implemented as executablelogic that is encoded in one or more non-transitory tangible media forexecution (e.g., programmable logic arrays or devices, fieldprogrammable gate arrays, programmable array logic, application specificintegrated circuits, etc.). Hence, one or more non-transitory tangiblemedia can be encoded with logic for execution by a machine, and whenexecuted by the machine operable for the operations described herein.

In addition, the operations described with respect to any of the Figurescan be performed in any suitable order, or at least some of theoperations can be performed in parallel. Execution of the operations asdescribed herein is by way of illustration only; as such, the operationsdo not necessarily need to be executed by the machine-based hardwarecomponents as described herein; to the contrary, other machine-basedhardware components can be used to execute the disclosed operations inany appropriate order, or execute at least some of the operations inparallel.

Referring to FIG. 4A, the processor circuit 32 of the root networkdevice 12 in operation 40 can establish the DODAG 20, for example instoring mode or nonstoring mode, based on outputting a DIO controlmessage specifying the prescribed objective function (OF), for exampleas described in RFC 6550, and specifying that multicasting is enabled(e.g., “Mode of Operation” (MOP) “3” in RFC 6550).

The processor circuit 32 of the root network device 12 in operation 40also can establish the LLN 10, for example in a CG-Mesh network, basedon a network joining process that can include: (1) PAN selection, wherea joining node 14 either listens for a discover beacon or sends out adiscover beacon request to select a Personal Area Network (PAN); (2)Authentication, where a joining node 14 can perform 802.1x mutualauthentication and obtain security keys from the Root and/or a parentnetwork device, or other authentication device; (3) PAN configurationwhere a joining node 14 either listens for a configuration beacon orsends out configuration beacon request to obtain PAN-wide information,such as broadcast schedule, PAN version; and (4) Routing formation,where a joining node 14 obtains an IPv6 address and advertises it to theFAR Root device 12 to configure a downward route from the FAR rootdevice to the joining node 12.

Assuming a RPL-based DODAG 20 is formed in operation 40, the processorcircuit 32 of the root network device 12 in operation 40 can learn apath to a network device “R” 14 in a limited region 22 (e.g., within anidentified meter “vault” in an identifiable building) that can operateas a multicast origin for multicast transmission of one or moremulticast data messages 24 within the limited region 22 of the DODAG 20,for example based on DAO messages from each of the LLN devices 14. Inone example, the root network device 12 can implement the DODAG 20 innonstoring mode, ensuring the root network device 12 can obtain a DAOmessage from each LLN device 14 for learning of topology parametersassociated with each limited region 22 in the DODAG 20; alternately, theroot network device 12 can implement the DODAG 20 in storing mode, whereeach “gateway” device (e.g., “L” and/or “F”) for a corresponding limitedregion 22 can send selected topology parameters associated with thelimited region 22 to the root network device 12.

Following establishment of the DODAG 20, the root network device 12 inoperation 42 can obtain a data message (e.g., from a network manager orheadend device, etc., not shown in the Figures) for localized multicastin the limited region 22: the data message can be supplied with anidentifier for the multicast origin (e.g., the LLN device “R”), or theroot network device 12 can select the multicast origin “R” 14, forexample in operation 44.

The processor circuit 32 of the root network device 12 in operation 44can determine the topology parameters and topology metrics for thelimited region 22 in the DODAG 20, including for example the ranges ofrank values between the “gateway” devices “F” and/or “L” and the rangesof rank values of each of the member LLN devices “L” through “W” thatbelong to the limited region 22. The processor circuit 32 of the rootnetwork device 12 in operation 44 can identify the LLN device “R” 14 asthe multicast origin for a multicast data message 24, and can set aminimum multicast (“m-cast”) distance value (e.g., “D=1” 46 of FIG. 5)that identifies the LLN device “R” 14 as a multicast origin; theprocessor circuit 32 of the root network device 12 in operation 44 alsocan set a distance limit value (e.g., “DL=249” 48 of FIG. 5), forexample based on determining (e.g., from prior messages received fromthe LLN devices 14) that the DODAG rank value for the gateway device “F”into the limited region 22 (as calculated by “F” during OF executionwhile joining the DODAG 20) is “Rank_F=100”, the DODAG rank value forthe LLN device “L” device in the limited region 22 (as calculated by “L”during OF execution while joining the DODAG 20) is “Rank_L=500”, and theDODAG rank value for the multicast origin LLN device “R” (as calculatedby “R” during OF execution while joining the DODAG 20) is “Rank_R=750”.

As described below, the distance limit value 48 set by the processorcircuit 32 of the root network device 12 in operation 44 can cause eachof the LLN devices “L” through “W” to limit multicast propagation of themulticast data message 24 to within the limited region 22, based oncausing an LLN device 14 receiving the multicast data message 24 tosuppress further multicast transmission of the received multicast datamessage 24 if the updated rank-based distance of the receiving LLNdevice 14 from the multicast origin “R” 14 in the limited region 22 isnot less than the distance limit value 48.

As illustrated in FIG. 2 the processor circuit 32 of the root networkdevice 12 in operation 46 of FIG. 4A can cause the device interfacecircuit 30 to unicast tunnel, to the LLN device “R” 14, the multicastdata message 24 within a unicast data message 26. The unicast datamessage 26 can specify the distance limit value 48 (e.g., “DL=249” 48 ofFIG. 5) that causes the multicast origin “R” 14 to limit the multicastpropagation to within the limited region 22. As illustrated in FIG. 4A,in one example operation 46 a the processor circuit 32 of the rootnetwork device 12 can generate (in operation 46 a) the multicast datamessage 24 that includes a distance limit field (50 of FIG. 5)specifying the distance limit value 48, and that further includes acurrent distance field (52 of FIG. 5) specifying the minimum distancevalue 46 to be used by the multicast origin “R” 14.

The processor circuit 32 of the root network device 12 in operation 46 balso can set the distance limit field 50 and the current distance field52 as separate data fields in the unicast data message 26 thatencapsulates the multicast data message 24 without the distance limitfield 50 or the current distance field 52 (enabling the multicast origin“R” 14 to dynamically insert the distance limit field 50 specifying thedistance limit value 48 and the current distance field 52 specifying theminimum distance value 46 into the multicast data message 24 prior toinitiating multicast transmission in the limited region 22, asappropriate).

The processor circuit 32 of the root network device 12 in operation 46 calso can specify within the unicast data message 26 a multicast flowidentifier associated with the multicast data message 24, enabling themulticast origin “R” 14 to store the minimum distance value 46 and thedistance limit value 48 and associated flow identifier in its memorycircuit 34, enabling the multicast origin “R” 14 to identify the sameminimum distance value 46 and distance limit value 48 for each multicastdata message 24 associated with the multicast flow identifier.

The device interface circuit 30 of the multicast origin “R” 14 canreceive in operation 48 the unicast data message 26 tunneled from theroot network device 12.

Referring to FIG. 4B, the processor circuit 32 of the multicast origin“R” 14 in operation 50 can parse the unicast data message 26 and detectthe multicast data message 24 encapsulated in the unicast data message26. The processor circuit 32 of the multicast origin “R” 14 in operation50 also can identify the minimum distance value 46 and the distancelimit value 48 to be used in the multicast data message 24 prior toinitiating multicast transmission in the limited region 22. As describedpreviously, in one example the processor circuit 32 of the multicastorigin “R” 14 in operation 50 can identify the distance limit value 48from the distance limit field 50 of the unicast data message 26 and/orthe encapsulated multicast data message 24, and the minimum distancevalue 46 specified in the current distance field 52 of the unicast datamessage 26 and/or the multicast data message 24; in another example theprocessor circuit 32 of the multicast origin “R” 14 in operation 50 canidentify the distance limit value 48 from a stored table entry (in itsmemory circuit 34) that stores multicast parameters (e.g., the minimumdistance value 46 and the distance limit value 48) associated with aprescribed multicast flow identifier.

The processor circuit 32 of the multicast origin “R” 14 in operation 52also can generate its own multicast data message 24, for example a localreset message within the “vault” 22 in response to a local administratorinput, etc., and in response obtain a locally-stored minimum distancevalue 46 and a locally-stored distance limit value 48.

The processor circuit 32 of the multicast origin “R” 14 in operation 54can insert (if needed) into a multicast data message 24 its minimumdistance value (e.g., “D=1”) 46 into a current distance field 52, andthe distance limit value (e.g., “DL=249”) 48 into the distance limitfield 50 of the multicast data message 24.

The processor circuit 32 of the multicast origin “R” 14 in operation 56also can optionally add a wireless transceiver tuning value (e.g., atransmit (“Tx”) power value) that is used by the device interfacecircuit 30 for wireless transmission of the multicast data message 24,and a multicast objective function identifier 56 that enables areceiving network device to calculate a multicast-based rank based onexecuting a multicast-based OF associated with the multicast objectivefunction identifier 56 and based on the link layer metrics including thetransmit power value 54, and a receive power value (e.g., RSSI)determined by the receiving LLN device 14.

The processor circuit 32 of the multicast origin “R” 14 in operation 56also can optionally add a current rank field 58 specifying the currentDODAG-based rank (e.g., “TxRank=750) 60, and a rank limit field 62specifying one or more of a minimum rank limit “R_MIN” 68 and/or amaximum rank limit “R_MAX” 64. As described below, the minimum ranklimit “R_MIN” 68 can limit upward flooding (toward the root networkdevice 12), and the maximum rank limit “R_MAX” 64 can limit downwardflooding (toward the leaves of the DODAG 20 inside the limited region22).

The processor circuit 32 of the multicast origin “R” 14 in operation 66can cause the device interface circuit 30 to initiate multicastpropagation of the multicast data message 24 by multicast transmittingthe multicast data message 24. As illustrated in FIG. 5, the multicastdata message 24 a output by the multicast origin “R” 14 comprises thecurrent distance field 52 specifying the minimum distance value 46 thatidentifies the LLN device “R” as the multicast origin, and the distancelimit field 50 specifying the distance limit “DL=249” 48. The multicastdata message 24 a also can comprise the transmit power value 54, themulticast objective function identifier 56, the current rank field 58specifying the DODAG-based rank 60, and the rank limit field 62specifying the minimum rank limit “R_MIN” and/or the maximum rank limit“R_MAX=825” 64.

Referring to FIG. 4C, the device interface circuit 30 of a receiving LLNdevice (e.g., “L”, “M”, “P”, “Q”, and/or “S”) in operation 70 canreceive the multicast data message 24 from one or more transmitting LLNdevices 14, for example the multicast data message 24 a from themulticast origin “R” 14. As illustrated in FIGS. 1, 2, and 5, over timemultiple LLN devices can multicast the multicast data message 24,resulting in a receiving LLN device (e.g., “M” or “Q”) 14 receivingmultiple copies of the multicast data message (e.g., 24 a, 24 b) fromdifferent transmitting LLN devices (e.g., the multicast origin “R” 14and the LLN device “P” 14), for example based on executing the Tricklealgorithm as described in RFC 7731. Hence the processor circuit 32 of areceiving LLN device 14 in operation 70 can wait for an identifiabletime interval (e.g., based on the Trickle algorithm as described in RFC6206) to determine whether to wait for an additional copy of themulticast data message 24 before proceeding with the operationsdescribed below.

Assuming reception of two or more multicast data messages 24 after anidentifiable time interval (e.g., based on the Trickle algorithm), theprocessor circuit 32 of the receiving LLN device 14 in operation 72 candetect a lowest distance limit value (designated “M-CAST MIN”),representing the multicast data message 24 having been transmitted fromnearest to the multicast origin “R” 14, among the absolute values of therespective current distance fields 52 of the received multicast datamessages 24. If only one multicast data message 24 is received after theidentifiable time interval (e.g., the LLN device “L” receives only theoriginal multicast data message 24 from the multicast origin “R” 14),the single minimum distance value 46 can be designated the lowestdistance limit value “M-CAST MIN”).

The processor circuit 32 of the receiving LLN device 14 in operation 72also can determine the distance limit value 48 from the distance limitfield 50 from any one of the received multicast data messages 24.

The processor circuit 32 of the receiving LLN device 14 in operation 74can determine the DODAG rank “Rank_n” of the neighboring LLN device “n”that multicast the multicast data message 24 with the lowest distancelimit value “M-CAST MIN”. In one example, the processor circuit 32 ofthe receiving LLN device 14 in operation 74 can determine whether thereceived multicast data message 24 specifies a current rank field 58that identifies the DODAG rank “Rank_n” 60; the processor circuit 32 ofthe receiving LLN device 14 in operation 74 also can determine the rank“Rank_n” of the neighboring LLN device “n” 14 from a neighbor table,stored in its memory circuit 34, that identifies respective ranks ofneighboring LLN devices 14 having previously advertised a DIO messageduring formation of the DODAG 20.

The processor circuit 32 of the receiving LLN device 14 in operation 76can determine its own rank “RxRank”: in one example, the processorcircuit 32 of the receiving LLN device 14 in operation 76 a can use itsDODAG rank value; in another example, the processor circuit 32 of thereceiving LLN device 14 in operation 76 b can calculate a multicastrank. In particular, the processor circuit 32 of the receiving LLNdevice 14 in operation 76 b can determine one or more receiver metrics(e.g., Received Signal Strength Indicator (RSSI), signal-to-noise ratio,bit error rate (BER), etc.) associated with receiving the multicast datamessage 24; the processor circuit 32 of the receiving LLN device 14 inoperation 76 b also can identify the multicast objective functionspecified by the multicast objective function identifier 56, and applythe receiver metrics and the transmit power value 54 specified in thereceived multicast data message 24 to determine the multicast rank to beapplied as the receiver rank “RxRank”.

The processor circuit 32 of the receiving LLN device 14 in operation 78can determine its updated distance “D” to the multicast origin “R” 14based on adding to the lowest distance value “D=M-CAST MIN” (obtainedfrom the current distance field 52 of the received multicast datamessage 24 in operation 72) the rank difference between thecorresponding neighboring transmitting LLN device “Rank_n” (determinedin operation 74) and the receiving LLN device 14 “RxRank”, i.e.,“D=D+(‘RxRank’−‘Rank_n’)”.

As illustrated in FIG. 5, the processor circuit 32 of the receivingnetwork device “P” 14 can determine that the current distance of thereceived multicast data message 24 a is “D=1” (based on the minimumdistance value 46 in the current distance field 52), and the rank of thetransmitting multicast origin “R” 14 is “Rank_R=750” (specified as theDODAG-based rank 60 in the current rank field 58 or obtained from theneighbor table); hence the receiving network device “P” 14 can determinein operation 78 (from its rank of “RxRank=700”) that its updateddistance is “D_P=1+(700−750)=−49” (a negative value indicating thereceiver is higher in the DODAG 20 than the transmitter).

The receiving network device “Q” 14 (having the DODAG rank “RxRank=850”)can determine in operation 78 (based on the received multicast datamessage 24 a) that its updated distance is “D_Q=1+(850−750)=101” (apositive value indicating the receiver is lower in the DODAG 20 than thetransmitter).

The receiving network device “S” 14 (having the DODAG rank “RxRank=600”)can determine in operation 78 (based on the received multicast datamessage 24 a) that its updated distance is “D_S=1+(600−750)=−149”.

The receiving network device “L” 14 (having the DODAG rank “RxRank=500”)can determine in operation 78 (based on the received multicast datamessage 24 from the multicast origin “R” 14) that its updated distanceis “D_L=1+(500−750)=−249”.

The processor circuit 32 of the receiving network device “L” 14 candetermine in operation 80 that the absolute value of its updateddistance “|D_L|=249” is not less than the distance limit value “DL=249”,i.e., “|D|=DL”. Hence, the processor circuit 32 of the receiving networkdevice “L” 14 in operation 82 suppresses transmission of the multicastdata message 24 in response to determining in operation 80 that thereceiving network device “L” is at the distance limit relative to themulticast origin “R” 14, i.e., that the updated distance of thereceiving network device “L” to the multicast origin “R” 14 (expressedas the absolute value “|D_L|”) is not less than the distance limit value“DL=249” 48 specified in the multicast data message 24. Hence, thesuppression of transmission by the receiving network device “L” 14prevents propagation of the multicast data message 24 beyond the limitedregion 22.

Depending on implementation preference, the distance limit value 48 alsocan be set such that the receiving network device “L” 14 can multicasttransmit the multicast data message 24 to the first-hop “gateway” device“F” 14 (e.g., if the distance value is set to “251”), but that thegateway device “F” that is outside the limited region 22 suppresses anytransmission of the multicast data message 24 outside the limited region22.

Hence, multicast transmissions of the multicast data message 24 can beexecuted within the limited region 22, while suppressing anytransmission of the multicast data message 24 outside the limited region22.

The processor circuit 32 of the receiving network device “P” 14 candetermine in operation 80 that the absolute value of its updateddistance “|D_P|=49” is less than the distance limit value “DL=249”,i.e., “|D|<DL”. In an optional operation 84, the processor circuit 32 ofthe receiving network device “P” 14 also can determine that itscorresponding DODAG rank “RxRank” is within the minimum rank limit“R_MIN=550” 68 and the maximum rank limit “R_MAX=825” 64, based ondetermining the DODAG-based rank 60 in the current rank field 58 of thereceived multicast data message 24 a, and adding the rank difference(“step of rank”) to the DODAG-based rank 60 of the transmittingmulticast origin “R” 14, i.e., “(RxRank−Rank_R)+TxRank”, or“(700−750)+750=700” which falls within the range of “550<700<825”.

Hence, the processor circuit 32 of the receiving network device “P” 14in operation 86 can update the relevant fields of the multicast datamessage 24 a, including the current distance field 52 to specify adistance of “D=−49”, the current rank field 58, and the transmit powervalue 54, and multicast transmit in operation 86 the multicast datamessage 24 b comprising the distance limit field 50 specifying thedistance limit value “DL=249” 48, and the updated fields including thecurrent distance “−49” in the current distance field 52. Similarly, thereceiving network device “S” (having the DODAG rank “RxRank=600”) candetermine in operation 80 that the absolute value of the updateddistance is less than the distance limit value, and determine inoperation 84 that the rank is within the limits 64 and 68, and inresponse multicast the multicast data message 24 c after updating therelevant fields as described above (including specifying the currentdistance field 52 with the current distance value “D=−149”).

In contrast, although the processor circuit 32 of the receiving networkdevice “Q” can determine that it is within the distance limit value 48in operation 80, the processor circuit 32 of the receiving networkdevice “Q” can determine in operation 84 that its rank “RxRank=850”exceeds the maximum rank limit “R_MAX” 64, hence the processor circuit32 of the receiving network device “Q” suppresses at least downwardtransmission of the multicast data message 24 in operation 82.Similarly, since the network devices “M” and “U” each have a DODAG rankof “525”, the network devices “M” and “U” can be within the distancelimit value 48 (“D=−224”) in operation 80, but the processor circuit 32of the network devices “M” and “U” can determine that theircorresponding rank “RxRank=525” is less than the minimum rank value of“R_MIN=550”, causing the network devices “M” and “U” to suppress atleast upward transmission of the multicast data message 24 in operation82.

Hence, the minimum rank limit “R_MIN” 68 can limit upward flooding(toward the root network device 12), and the maximum rank limit “R_MAX”64 can limit downward flooding (toward the leaves of the DODAG 20 insidethe limited region 22).

According to example embodiments, multicast transmissions can belocalized based on a rank-based distance relative to a multicast origin.The rank-based distance can be based solely on a DODAG-based rank, orcan be based on a multicast rank that is generated according to anobjective function optimized for localized multicast transmissions.

An additional embodiment can include an apparatus comprising a processorcircuit and a device interface circuit. The processor circuit isconfigured for identifying a minimum distance value to be used formulticast transmission as a low power and lossy network (LLN) device ina low power and lossy network (e.g., the minimum distance valueidentifying the apparatus as a multicast origin), the processor circuitfurther configured for identifying a distance limit value for limitingmulticast propagation, initiated at the LLN device, of a multicast datamessage in the LLN. The device interface circuit is configured formulticast transmitting the multicast data message with a currentdistance field specifying the minimum distance value and a distancelimit field specifying the distance limit value, the multicasttransmitting causing a receiving LLN device having a corresponding rankin the LLN to respond to the multicast data message by: (1) determiningan updated distance based on adding to the current distance field a rankdifference between the receiving LLN device and the LLN device, and (2)selectively retransmitting the multicast data message if the updateddistance is less than the distance limit value.

An additional embodiment can include an apparatus implemented as areceiving low power and lossy network (LLN) device in a low power andlossy network, the apparatus comprising a device interface circuit and aprocessor circuit. The device interface circuit is configured forreceiving one or more multicast data messages from respective one ormore neighboring transmitting LLN devices in the LLN. The processorcircuit is configured for detecting, among the one or more multicastdata messages, a lowest distance value in a current distance field and adistance limit value in a distance limit field, the lowest distancevalue indicating a multicast transmission distance of the correspondingone neighboring transmitting LLN device relative to a multicast originof the one or more multicast data messages. The processor circuit isconfigured for determining an updated distance to the multicast originbased on adding to the lowest distance value a rank difference betweenthe corresponding neighboring transmitting LLN device and the receivingLLN device. The processor circuit is configured for causing the deviceinterface circuit to selectively multicast transmit the multicast datamessage based on the processor circuit determining the updated distanceis less than the distance limit value that limits multicast propagation.The processor circuit further is configured for updating the currentdistance field with the updated distance value prior to transmission ofthe multicast data message.

An additional embodiment can include an apparatus implemented as a rootnetwork device in a low power and lossy network (LLN), the apparatuscomprising a processor circuit and a device interface circuit. Theprocessor circuit is configured for limiting multicast propagation of amulticast data message in the LLN based on setting a distance limitvalue for limiting the multicast propagation, and further based ongenerating a unicast message containing the multicast data message andthe distance limit value. The processor circuit is configured forcausing the device interface circuit to unicast transmit the unicastmessage containing the multicast data message and the distance limitvalue to an LLN device via the LLN. The unicast message causes the LLNdevice to multicast transmit the multicast data message with a currentdistance field specifying a minimum distance value of the LLN device anda distance limit field specifying the distance limit value. Theprocessor circuit causes the limiting multicast propagation in the LLNbased on causing a receiving LLN device having a corresponding rank inthe LLN to respond to the multicast data message by: (1) determining anupdated distance based on adding to the current distance field a rankdifference between the receiving LLN device and the LLN device, and (2)selectively retransmitting the multicast data message if the updateddistance is less than the distance limit value, wherein the receivingLLN device suppresses any transmission of the multicast data message ifthe updated distance is not less than the distance limit value.

While the example embodiments in the present disclosure have beendescribed in connection with what is presently considered to be the bestmode for carrying out the subject matter specified in the appendedclaims, it is to be understood that the example embodiments are onlyillustrative, and are not to restrict the subject matter specified inthe appended claims.

What is claimed is:
 1. A method comprising: identifying, by a low powerand lossy network (LLN) device in a low power and lossy network, aminimum distance value and a distance limit value for limiting multicastpropagation, initiated at the LLN device, of a multicast data message inthe LLN; and multicast transmitting, by the LLN device, the multicastdata message with a current distance field specifying the minimumdistance value and a distance limit field specifying the distance limitvalue, the multicast transmitting causing a receiving LLN device havinga corresponding rank in the LLN to respond to the multicast data messageby: (1) determining an updated distance based on adding to the currentdistance field a rank difference between the receiving LLN device andthe LLN device, and (2) selectively retransmitting the multicast datamessage if the updated distance is less than the distance limit value;the multicast transmitting including transmitting, with the multicastdata message, a current rank field specifying a corresponding rank ofthe LLN device and a rank limit field specifying a rank limit; the ranklimit field causing the receiving LLN device to selectively limit one ormore of upward flooding or downward flooding of the multicast datamessage in the LLN based on the corresponding rank of the receiving LLNdevice relative to the current rank field and the rank limit.
 2. Themethod of claim 1, further comprising inserting into the multicast datamessage, by the LLN device, the minimum distance value into the currentdistance field and the distance limit value into the distance limitfield.
 3. The method of claim 1, further comprising inserting into themulticast data message, by the LLN device, a wireless transceiver tuningvalue and a multicast objective function identifier; the multicastobjective function identifier causing the receiving LLN device todetermine the corresponding rank as a multicast rank based on thewireless transceiver tuning value and receiver metrics determined by thereceiving LLN device.
 4. The method of claim 3, wherein the wirelesstransceiver tuning value is a transmit power value of a wirelesstransceiver of the LLN device.
 5. The method of claim 1, wherein therank limit identifies one or more of a minimum rank limit for limitingupward flooding to an LLN device having the minimum rank limit as itscorresponding rank, or a maximum rank limit for limiting downwardflooding to an LLN device having the maximum rank limit as itscorresponding rank.
 6. The method of claim 1, further comprising:receiving, by the LLN device, a unicast packet tunneled from a sourcedevice and comprising the multicast data message; the identifyingincluding parsing the unicast packet and detecting the multicast datamessage, the detecting causing the LLN device to multicast transmit themulticast data message.
 7. One or more non-transitory tangible mediaencoded with logic for execution by a machine and when executed by themachine operable for: identifying, by the machine implemented as a lowpower and lossy network (LLN) device in a low power and lossy network, aminimum distance value and a distance limit value for limiting multicastpropagation, initiated at the LLN device, of a multicast data message inthe LLN; and multicast transmitting, by the LLN device, the multicastdata message with a current distance field specifying the minimumdistance value and a distance limit field specifying the distance limitvalue, the multicast transmitting causing a receiving LLN device havinga corresponding rank in the LLN to respond to the multicast data messageby: (1) determining an updated distance based on adding to the currentdistance field a rank difference between the receiving LLN device andthe LLN device, and (2) selectively retransmitting the multicast datamessage if the updated distance is less than the distance limit value;the multicast transmitting including transmitting, with the multicastdata message, a current rank field specifying a corresponding rank ofthe LLN device and a rank limit field specifying a rank limit; the ranklimit field causing the receiving LLN device to selectively limit one ormore of upward flooding or downward flooding of the multicast datamessage in the LLN based on the corresponding rank of the receiving LLNdevice relative to the current rank field and the rank limit.
 8. The oneor more non-transitory tangible media of claim 7, wherein the rank limitidentifies one or more of a minimum rank limit for limiting upwardflooding to an LLN device having the minimum rank limit as itscorresponding rank, or a maximum rank limit for limiting downwardflooding to an LLN device having the maximum rank limit as itscorresponding rank.
 9. The one or more non-transitory tangible media ofclaim 7, further operable for: receiving, by the LLN device, a unicastpacket tunneled from a source device and comprising the multicast datamessage; the identifying including parsing the unicast packet anddetecting the multicast data message, the detecting causing the LLNdevice to multicast transmit the multicast data message.
 10. The one ormore non-transitory tangible media of claim 7, further operable forinserting, into the multicast data message, the minimum distance valueinto the current distance field and the distance limit value into thedistance limit field.
 11. The one or more non-transitory tangible mediaof claim 7, further operable for: inserting, into the multicast datamessage, a wireless transceiver tuning value and a multicast objectivefunction identifier; the multicast objective function identifier causingthe receiving LLN device to determine the corresponding rank as amulticast rank based on the wireless transceiver tuning value andreceiver metrics determined by the receiving LLN device.
 12. The one ormore non-transitory tangible media of claim 11, wherein the wirelesstransceiver tuning value is a transmit power value of a wirelesstransceiver of the LLN device.
 13. An apparatus implemented as aphysical machine, the apparatus comprising: non-transitory machinereadable media configured for storing executable machine readable code;a device interface circuit; and a processor circuit configured forexecuting the machine readable code, and when executing the machinereadable code operable for: identifying, by the apparatus implemented asa low power and lossy network (LLN) device in a low power and lossynetwork, a minimum distance value and a distance limit value forlimiting multicast propagation, initiated at the LLN device, of amulticast data message in the LLN, and multicast transmitting themulticast data message with a current distance field specifying theminimum distance value and a distance limit field specifying thedistance limit value, the multicast transmitting causing a receiving LLNdevice having a corresponding rank in the LLN to respond to themulticast data message by: (1) determining an updated distance based onadding to the current distance field a rank difference between thereceiving LLN device and the LLN device, and (2) selectivelyretransmitting the multicast data message if the updated distance isless than the distance limit value; the multicast transmitting includingtransmitting, with the multicast data message, a current rank fieldspecifying a corresponding rank of the LLN device and a rank limit fieldspecifying a rank limit; the rank limit field causing the receiving LLNdevice to selectively limit one or more of upward flooding or downwardflooding of the multicast data message in the LLN based on thecorresponding rank of the receiving LLN device relative to the currentrank field and the rank limit.
 14. The apparatus of claim 13, whereinthe processor circuit is configured for inserting into the multicastdata message the minimum distance value into the current distance fieldand the distance limit value into the distance limit field.
 15. Theapparatus of claim 13, wherein the processor circuit is configured forinserting into the multicast data message a wireless transceiver tuningvalue and a multicast objective function identifier; the multicastobjective function identifier causing the receiving LLN device todetermine the corresponding rank as a multicast rank based on thewireless transceiver tuning value and receiver metrics determined by thereceiving LLN device.
 16. The apparatus of claim 15, wherein thewireless transceiver tuning value is a transmit power value of awireless transceiver of the LLN device.
 17. The apparatus of claim 13,wherein the rank limit identifies one or more of a minimum rank limitfor limiting upward flooding to an LLN device having the minimum ranklimit as its corresponding rank, or a maximum rank limit for limitingdownward flooding to an LLN device having the maximum rank limit as itscorresponding rank.
 18. The apparatus of claim 13, wherein the processorcircuit is configured for: receiving a unicast packet tunneled from asource device and comprising the multicast data message; the processorcircuit configured for parsing the unicast packet and detecting themulticast data message, the detecting causing the LLN device tomulticast transmit the multicast data message.